You can track your FBA customer returns using the LPN RR number on the product (usually located near UPC or barcode) and your sales report.
Learn how to read Amazon's FBA Inventory Reconciliation Report.
Amazon's refund administration fee explained for new sellers here.
Follow the link below to see all of Amazon's FBA fees.
Follow the link below to Amazon's FBA profit calculator.
Learn how to find the ship to address on Amazon for orders with confidential or missing shipping addresses.